check-versions.js

  //定制控制台日记的输入款式
  var chalk = require('chalk')
    // 加载语义化版本测试库
  var semver = require('semver')
    // 引入package.json文件
  var packageConfig = require('../package.json')
  function exec(cmd) {
    // require('child_process')挪用nodejs子历程，
    // execSync同步的exec要领实行command
    return require('child_process').execSync(cmd).toString().trim()
  }
  var versionRequirements = [{
    name: 'node',
    // process.version是当前运用的node版本信息'v7.1.0'
    // semver.clean('  =v1.2.3   ')返回'1.2.3'
    // semver.clean(process.version)格式化返回当前运用的node版本信息'7.1.0'
    currentVersion: semver.clean(process.version),
    // 从package.json读取node版本请求
    versionRequirement: packageConfig.engines.node
  }, {
    name: 'npm',
    currentVersion: exec('npm --version'),
    // 从package.json读取npm版本请求
    versionRequirement: packageConfig.engines.npm
  }]
  module.exports = function() {
    var warnings = []
    for (var i = 0; i < versionRequirements.length; i++) {
      var mod = versionRequirements[i]
        // 推断现有版本是不是满足请求
      if (!semver.satisfies(mod.currentVersion, mod.versionRequirement)) {
        warnings.push(mod.name + ': ' +
          chalk.red(mod.currentVersion) + ' should be ' +
          chalk.green(mod.versionRequirement)
        )
      }
    }
    // 打印错误信息
    if (warnings.length) {
      console.log('')
      console.log(chalk.yellow('To use this template, you must update following to modules:'))
      console.log()
      for (var i = 0; i < warnings.length; i++) {
        var warning = warnings[i]
        console.log('  ' + warning)
      }
      console.log()
      // 根据linux的范例，平常成服从0示意，而非0则示意失利。存在不满足版本请求的模块，实行失利
      process.exit(1)
    }
  }